1. Field of the Invention
The present general inventive concept relates to a system, apparatus and method to control the output of a radio frequency (RF) signal, and more particularly, to a system, apparatus and method to automatically control the output of an RF signal according to local characteristics by establishing a particular field of a frame for wireless communication as information to control the output of the RF signal.
2. Description of the Related Art
Wireless terminal apparatuses complying with a wireless local area network (LAN) standard such as the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard usually use an RF signal in the 2.4 or 5 GHz band. When using wireless terminal apparatuses, users need to be cautious since such RF signals cause errors in other electronic machines. In particular, use of wireless terminal apparatuses should be restricted in places such as airplanes, hospitals, and laboratories. US Federal Aviation Administration recommends the installation of an ON/OFF button for controlling the output of an RF signal to wireless terminal apparatuses complying with the wireless LAN standard, so that a user can control RF transmission and reception by directly operating the ON/OFF button in places where output of RF signals is restricted.
FIG. 1A illustrates a conventional hardware structure for controlling the output of an RF signal. A wireless terminal apparatus includes an RF switch 100 which controls the output of an RF signal and a wireless LAN module 120 which transmits and receives RF signals. In other words, a user inputs an ON or OFF signal using the RF switch 100 that can be directly operated by the user, and then the ON or OFF signal connects to a particular pin of the wireless LAN module 120 and directly controls the output of an RF signal. Alternatively, a microcomputer 110 may receive a signal for controlling output of RF signals from the RF switch 100 and control the wireless LAN module 120. For example, when a function key of a notebook computer is used, the microcomputer 110 may sense a user's input and control the output of an RF signal generated by the wireless LAN module 120 using an interface such as a General Purpose Interface Bus (GPIB).
FIG. 1B illustrates a conventional software structure for controlling the output of an RF signal. If a user sets a value in an application 150, which provides a function that controls the output of an RF signal, enabling the output of an RF signal to be controlled, a driver 160 controlling a wireless LAN module 170 controls the output of an RF signal by the wireless LAN module 170 using the value.
FIG. 2A is a flowchart of a conventional method of controlling the output of an RF signal in a hardware manner.
After turning on the power of a wireless terminal apparatus in step S200, if a user sets a switch for controlling the output of an RF signal in the on position in step S205, an RF-on signal for permitting the output of an RF signal is transmitted to an RF module in step S210. However, if the user sets the switch in the off position, an RF-off signal for interrupting the output of an RF signal is transmitted to the RF module in step S215.
FIG. 2B is a flowchart of a conventional method of controlling the output of an RF signal in a software manner.
After turning on the power of a wireless terminal apparatus in step S250, if a user makes configuration changes in an application which can control the output of an RF signal to control the output of an RF signal in step S255, configuration information is transmitted to a driver which controls an RF module in step S260. If the configuration information permits the output of an RF signal in step S265, an RF signal is allowed to be output by the RF module in steps S280 and S285. However, if the configuration information interrupts the output of an RF signal in S265, the output of an RF signal is interrupted by the RF module in steps S270 and S275.
However, when a user is not cautious or is inexperienced at operating a wireless terminal apparatus, or when the above-described recommendation is not followed, there still remains a risk that an RF signal may be output and have an affect in places where the output of an RF signal is restricted. Moreover, since the user needs to personally control the output of an RF signal, the user may feel inconvenienced.
Therefore, it is desirable that under a predetermined condition, the output of an RF signal, which is generated by a wireless terminal apparatus, be automatically controlled without a user's personal operation or intervention.